Semiconductor devices are being widely used in electronic products. For example, a thin film transistor, as one example of a semiconductor device, is a switching device having a gate electrode, source electrode, and drain electrode. It is being widely used for active devices of active matrix boards of active matrix type liquid crystal displays or organic EL and other display devices.
In conventional thin film transistors, sputtering, vapor deposition, or CVD was used to form a passivation film (protective film) comprised of a silicon nitride film (SiNx film) on the surface of the semiconductor layer. However, in the method of forming a passivation film comprised of an inorganic material such as a silicon nitride film, there were the problems that the passivation film had to be formed in the state of plasmatising or ionizing the material in the vacuum, the equipment was large in size, and the operation was complicated. Further, if removing the passivation film comprised of an inorganic material or changing the material or method of production to a material or method enabling formation of a film by a method of a simpler process, there was the problem that the reliability became poor.
As opposed to this, for example, Patent Document 1 proposes a method of forming a passivation film of a thin film transistor by an organic material. In this Patent Document 1, as the organic material for forming the passivation film, a heat cross-linkable resin composition containing at least one type of resin selected from a cyclic olefin polymer, acrylic resin, cardo resin, polysiloxane, or polyimide and a cross-linking agent has been used. However, this Patent Document 1 is art using a semiconductor layer comprised of an amorphous silicon layer. For example, if the semiconductor layer is formed by using an indium gallium zinc oxide (IGZO) or other inorganic oxide semiconductor, there were the problems that the absolute value of the threshold voltage Vth ended up becoming larger and the mobility ended up falling.